With the development of communication technology, LTE-A (Long Term Evolution Advanced) system has witnessed great improvement of peak rate compared with LTE (Long Term Evolution), and is required to reach 1 Gbps downlink and 500 Mbps uplink. Meanwhile, LTE-A system needs better compatibility with LTE system. In consideration of the improved peak rate, compatibility with LTE system and full use of spectrum resource, CA (Carrier Aggregation) technique is imported in LTE-A system.
Carrier aggregation technology means that a terminal can work on a plurality of cells at the same time and a cell comprises a pair of UL/DL (Uplink/Downlink) CC (Component Carrier) or independent DL carrier, rather than that there is only one set of carrier in the LTE system and previous wireless communication system. In the carrier aggregation system, component carriers can be continuous or discontinuous and the bandwidths of each component carriers can be the same or different. To be compatible with the LTE system, maximum bandwidth of each component carrier is limited as 20 MHz. At present, the maximum number of the cell/CC aggregated of an UE is generally considered as 5.
In addition, the cells of LTE-A is classified as:
(1) Primary cell: only one cell among the cells aggregated of UE (User Equipment) is defined as Primary cell.
(2) Secondary cell: refers to other cells aggregated of the UE other than the Primary cell.
Primary cell is selected by a base station and is configured for the terminal through a RRC (Radio Resource Control) signaling. Different terminals can be configured with different Primary cells. A PUCCH (Physical Uplink Control Channel) is configured on a UL CC of the Primary cell, and is not configured on the UL CC of the Secondary cell.
In prior art, structural diagram for a packet data unit (PDU) of a MAC (Media Access Control) layer in the LTE system is shown in FIG. 1.
In the figure, the case that a MAC PDU comprises a MAC header, a MAC SDU (Service Data Units), a MAC CE (Control Element) and a padding is marked out.
The MAC PDU has the following basic characteristcis:
The MAC header is composed of one or a plurality of MAC sub-header (s); each MAC sub-header is corresponding to a MAC SDU or a MAC CE or a padding;
Length of the MAC header and the MAC SDU is variable;
Byte alignment is required for the MAC sub-header, MAC SDU and MAC CE;
The correspondence between sequence of a bit stream of the MAC PDU from high level to low level and structural drawing of the MAC PDU in the agreement is: the reading sequence from left to right and from up to down;
Sequence of MAC CE/MAC SDU/padding in the MAC PDU is shown as below: the MAC CE is the foremost, but the MAC CE of a padding BSR (Buffer Status Reports) is excepted; MAC SDU next and finally the padding (the padding BSR is the last one in the MAC PDU);
Sequence of the sub-header corresponding to MAC CE/MAC SDU/padding in the MAC is in consistent with the sequence in the MAC PDU.
PHR (Power Headroom Reporting) is such a mechanism that the UE reports a difference between UE sending power and the maximum power to a base station.
In an LTERel-8/9 system, PH (Power Headroom) is defined aiming to a PUSCH (Physical Uplink Shared Channel) as below:PH=PCmax−PPUSCH 
Wherein:
PCmax represents the maximum transmission power allowed in the case the terminal meeting radio frequency index.
PPUSCH represents the transmission power of the terminal.
In the LTE Rel-8/9 system, the PH is reported via. a PHR MAC CE. The PHR MAC CE comprises a MAC sub-header and a MAC CE. The structural diagram of the MAC sub-header and MAC CE is respectively shown in FIG. 2 and FIG. 3.
Wherein, meaning of all fields is shown as below:
A LCID (Logical Channel Identity) field: is used to identify a logical channel number of corresponding load part. For a PHR process, the LCID is used to identify the corresponding load part, that is, the PHR. The LCID corresponding to a LTE Rel-8/9 PHR is 11010, as shown in Table 1:
TABLE 1Identification of Uplink LCIDIndexLCID values00000CCCH00001-01010Identity of the logical channel01011-11001Reserved11010Power Headroom Report11011C-RNTI11100Truncated BSR11101Short BSR11110Long BSR11111Padding
Wherein:
E field: represents expanded bit, which is used to indicate which one the next byte is, the MAC sub-header or a MAC load
R field: represents the reserved bit.
PH field: represents the uplink power headroom.
Furthermore, description of the PHR in the LTE-A system is made as following:
I. PH Calculation Mechanism
At present, LTE-A is generally considered to have two calculation modes for PH:
Mode I: Per CC PHR (Reporting the PHR Based on the CC)
In such mode, the PH is calculated aiming to the CC. Since different PUCCH channels are configured, different types of PHR is defined by the LTE-A aiming to the Primary cell and Secondary cell, which is specifically shown as below:
(1) The PHR of Type 1 and Type 2 is defined for the Primary cell; wherein,Type 1: PHRPUSCH=Pcmax,c−PPUSCH Type 2: PHRPUCCH+PUSCH=Pcmax,c−PPUSCH−PPUCCH (2) Since PUCCH is unavailable for the UL CC, only Type 1 PHR is defined for the Secondary cell:Type 1: PHRPUSCH=Pcmax,c−PPUSCH Mode II: Per UE PHR (Reporting the PHR Based on the UE)
For formula has not been determined at present. A possible mode is:PHRUE=Pcmax−PPUSCH1−PPUSCH2− . . . −PPUSCHn−PPUCCH−multiple_CC_MPR 
Wherein:
PPUSCHn represents the PUSCH power on carrier CCn configured for the UE;
multiple_CC_MPR: represents a MPR (Maximum Power Reduction) caused by the transmission of a plurality of CC;
Which PHR of the UL CC needs to be reported to the UE should be considered for both the per CC PHR in mode I and the per UE PHR in mode II. Three options are provided generally:
(1) Determine the n according to number of the UL CC configured by the base station for the UE;
(2) Determine the n according to number of the UL CC activated configured by the base station for the UE;
(3) Determine the n according to number of the UL CC with the UL grant that the base station allocates for the UE;
For the (1) and (2) above, when the UE does not have real PUCCH or PUSCH on a certain UL CC, a prior method adopted is to import a concept of “virtual PUCCH or PUSCH”. That is to say calculate power of the virtual PUCCH or PUSCH by using a certain reference format. In other words, if the UE can not receive the UL grant, a virtual PHR will be calculated according to virtual PUCCH or PUSCH reference format; the real PHR will only be reported only when the real UL grant is received.
II. PH Reporting Mechanism
At present, conclusion of reporting PHR Type on the Primary cell and Secondary cell is made as follows:
(1) Only Type 1 PHR is reported on the Secondary cell.
(2) When the PUCCH and PUSCH energe at the same time on the Primary cell, the Type 1 PHR and the Type 2 PHR should be reported simultaneously.
(3) When the PUCCH and PUSCH do not emerge at the same time on the Primary cell, the conclusion whether the Type 1 PHR and the Type 2 PHR are reported simultaneously has not been made.
At present, it is inclined to that a per CC PHR on each CCs in LTE-A system will be reported at the same time if any PHR of the UE is triggered; moreover, some companies suggest reporting a per UE PHR when reporting the per CC PHR on each CC.
During implementation of the embodiments of the present invention, the applicant finds that the following problems at least exist in the available technology:
Compared with the LTE Rel-8/9, more information should be comprised for reporting of the PH in the LTE-A multiple carrier system. For example:
(1) A LTE-A CA UE is required to report the PH information of a plurality of CCs and number of the CCs can change in semi-static state or dynamically.
(2) A PHR triggering mechanism of a CA UE may be in the UE level, viz. once the PHR triggering condition is met, the per CC PH information of a plurality of CCs is required to be reported to the base station by the UE when needing to report the PHR.
(3) The Primary cell is required to distinguish whether the Type 1 PHR and the Type 2 PHR are reported at the same time.
(4) If per UE PHR exists, it is still required to distinguish UE PH information from CC PH information.
In addition, if the PH is reported based on all the UL CC with the UL grant of the UE, another problem will be brought in, viz. if the base station sends the UL grant, but the UE does not receive it, the UE will adopt the virtual PHR and the base station will consider the PHR received a the real PHR, which will cause inconsistent understanding of the base station and the UE. So PHR is required to distinguish the real from the virtual PHR.
To sum up, the PHR MAC CE format of the LTE Rel-8/9 is not applicable and a new format needs to be considered for the CA system.